The present invention relates generally to a Z-axis lifting technique, and more particularly to a lifting mechanism with self-locking function.
Various lifting techniques have been developed for ascending/descending a load in the direction of Z-axis. For example, a power output shaft of a power source such as a motor or a hydraulic cylinder can be used to directly apply a force to the load and move the load in the direction of Z-axis. Alternatively, the power source can drive the load and move the load in the direction of Z-axis via a reduction mechanism such as a worm and a worm wheel. When the load is lifted to a high position, the power source can keep the load at the height by its own holding capability. Alternatively, the load can be lifted by means of wedge structures with guide slopes in slidable contact with each other. The guide slopes have a certain inclination angle and serve to convert the horizontal sliding force into the lifting force in the direction of Z-axis to save strength and reduce the speed.
The conventional lifting apparatuses are applicable to various fields. However, such lifting apparatuses are not optimal and have some defects. For example, with respect to the direct-drive technique, the power source must be continuously powered on to provide the necessary power. With respect to the transmission technique of the worm and worm wheel, it is impossible to apply such technique to a vacuumed or clean room. With respect to the wedge structures, such structures have poor self-locking capability. When the load is stopped on the guide slopes or during the lifting process of the load, the lead angle must be gradually decreased until nearly horizontal. Under such circumstance, the vertical component force is much smaller than the horizontal component force so as to achieve self-locking effect. According to such arrangement, the volume of the apparatus is increased as a whole. Moreover, it cannot be ensured that the load stably stops on the guide slopes. In some cases, the load may displace due to vibration or change of vertical loadability. Therefore, it is impossible for such conventional lifting apparatus to have secure self-locking effect in any position.